Description

Implements the following refactoring improvements:

1. StorageService - a centralized, easy to access class that stores various types of information that our driver uses, eg custom endpoint info and topology info.
2. MonitorService - a centralized, easy to access class that standardizes the submission and lifetime of the various monitors that our driver creates, eg custom endpoint monitors and topology monitors. Submitted monitors are stored under this service.
3. ConnectionService - replaces the forceConnect functionality, providing the ability to create auxiliary ConnectionWrapper objects that no longer share a PluginService with the connection that is requesting the auxiliary connection.
4. EventPublisher/EventSubscriber - a publish-subscribe pattern that allows the communication of generic events between interested driver components.

So far, the custom endpoint and topology caches and monitors have been adapted to use the StorageService and MonitorService. In the future, more caches and monitors will be adapted as well.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.